1. Field of the Invention
This invention relates generally to latch apparatus and more specifically to a latch adapted for use in an emergency debarkation system of an aircraft.
2. Description of the Prior Art
Commercial aircraft are required by the regulations of the Federal Aviation Administration to have an emergency debarkation system. Such a system is designed to provide for the emergency evacuation of all personnel in the aircraft when the stairways and tunnels commonly used at airports are not available. Such an emergency debarkation system might be employed when an aircraft is forced to land at other than an airport, either on the land or in the water.
These emergency debarkation systems commonly includes slides, which are designed to extend from an elevated hatch of the aircraft down to surface level. For emergency debarkation in water, the system will commonly includes slides or slide/rafts. These slides or slide/rafts are typically of the type which include bottles of pressurized gas for automatically inflating the slides or rafts.
The slides or slide/rafts are normally packaged in a deflated state in a container having two major portions which are hinged with respect to each other and mounted on doors or hatches at emergency exits of the aircraft.
It is desirable that these containers be provided with latches which can withstand significant forces acting in certain axes of the aircraft which tend to open the containers. At the same time, it is desirable that the latches be openable in response to relatively small forces acting in other certain axes of the aircraft in order to permit the slide or slide/raft to fall free of the container. It is further desirable that the latches be simple to set. Preferably, a single person should be able to load the slide or slide/raft in the associated container and set the latch with the container mounted on the emergency door.
The latch should be highly reliable as is the case with all aircraft equipment. Under normal circumstances, it must remain latched even though exposed to excessive vibrations, accelerations and contaminations. However, under emergent conditions, it is desirable that the latch be automatically operable to unlock the container and the deploy the associated slide or slide/raft.
If one latch apparatus of the prior art, first and second latch members are fixed to the respective major portions of the container. Each of the latch members includes a pair of parallel spring arms which extend toward the arms of the opposite latch member. Each of the spring arms in each of the latch members is provided with a hole.
The latch assembly is provided with an over-center toggle which has a pair of pins which extend in opposite directions. To set the latch, the toggle pins can be disposed in the holes of the spring arms associated with the first latch members. Then the toggle can be pushed over center. This procedure typically requires a significant amount of force and often causes injury to the user resulting from the pinching of his fingers. When the toggle is in place, the pins of the toggle protrude through the holes of the first latch member.
Once the toggle is mounted in the first latch member, the container can be shut. As the major members of the container are brought together, the holes associated with the arms in the second latch member are pressed over the protruding pins of the toggle. This too requires a significant amount of force. To operate the latch and open the container, a lanyard is provided to pull the toggle over center and to remove the pins from the holes in the arms of the latch members.
Due to the difficulty of the technique and the significant forces required for mounting the toggle, the setting of this latch of the prior art has typically required two persons. For example, to set the latch, the container has typically been removed from the door so that one person can stand on the container while the other person sets the latch. To reduce the significant forces required, there has been a great tendency to relieve some of the pressure on the arms associated with the latch members. This has typically been accomplished by bending the arms. Such a procedure has weakened the latch so that it has commonly opened with only minimal vibrations or accelerations such as those caused by merely hitting the container. In addition to unlocking the latch, this has resulted in opening the container so that the slide or slide/raft has fallen onto the floor of the aircraft. Not only must the container be reloaded and the latch reset, but until this is accomplished, these units are not ready for use in the event of an emergency.
In some cases, the over-center toggles have been jammed. With each of the pins of the toggles extending through a pair of closely spaced holes in opposing arms of the latch, the pins experience significant sheer forces which tend to bind the pins in the holes. Since these latches are seldom checked, this jamming of the latch would normally go undetected until an emergency occurred. The jamming of the latch at that time would be quite intolerable.